Circ: Near-infrared spectroscopy aids with lipid-core plaque detection

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Near-infrared spectroscopy (NIRS) provides rapid, automated detection of extensive lipid-core plaques (LCP) that are associated with a high risk of periprocedural MI, presumably due to embolization of plaque contents during coronary intervention, according to a substudy of the COLOR registry, published in the October issue of Circulation: Cardiovascular Interventions.

The study was conducted in a subset of cases enrolled in the COLOR Registry, an ongoing, prospective multicenter observational study of patients undergoing NIRS (LipiScan, InfraReDx) before PCI.

PCI is associated with periprocedural MI in 3 percent to 15 percent of cases (depending on the definition used), according to the study authors. In many cases, these MIs result from distal embolization of LCP constituents. Prospective identification of LCP with catheter-based NIRS may predict an increased risk of periprocedural MI and facilitate development of preventive measures.

James A. Goldstein, MD, from the department of cardiovascular medicine at William Beaumont Hospital in Royal Oak, Mich., and colleagues analyzed the relationship between the presence of a large LCP (detected by NIRS) and periprocedural MI. Patients with stable preprocedural cardiac biomarkers undergoing stenting were identified from the COLOR Registry. 

The extent of LCP in the treatment zone was calculated as the maximal lipid-core burden index measured by NIRS for each of the 4 mm longitudinal segments in the treatment zone, according to the researchers. A periprocedural MI was defined as new cardiac biomarker elevation above three times the upper limit of normal.

A total of 62 patients undergoing stenting met eligibility criteria. The primary finding of the study was that in patients with coronary artery disease, PCI of lesions with a large lipid core (maxLCBI4 mm greater than or equal to 500 by NIRS) is associated with a 50 percent risk of periprocedural MI, compared with only a 4.2 percent risk for lesions without a large lipid core (maxLCBI4 mm less than 500 by NIRS). 

“NIRS provided rapid, automated detection of these high-risk LCPs associated with culprit stenosis,” the authors wrote. “Conversely, lesions without a large lipid core had a low risk of periprocedural MI.”

They also noted that the present study of periprocedural MI adds to accumulating evidence that LCPs are associated with complications of stenting. In addition to the relationship with periprocedural MI, autopsy studies have demonstrated that stent thrombosis and restenosis often occur at sites of LCP.

“These findings demonstrate that large LCP identified by NIRS may provide improved risk assessment before coronary stenting,” Goldstein and colleagues concluded.

A randomized trial of embolic protection devices as a means to enhance the safety of coronary stenting in high-risk, stenotic LCPs as identified by NIRS is underway.